Warm, sunny weather brings out blue-green algae

Algae has been causing some odor problems on Little Rock Lake. The algae thrives in calm, warm weather experts say. Algae shown is near a boat launch on the lake Friday.
(Photo:
William Camargo, wcamargo@stclou
)

RICE – The recent stretch of warm, sunny, calm weather has brought some perfect days for enjoying Minnesota's lakes.

It's also created perfect conditions for a nuisance that plagues many of those lakes: blue-green algae, a sometimes toxic form that creates an ugly, smelly scum and can cause health problems for people and pets.

"We're getting into the kind of weather that really allows for the blue-green blooms to take off," said Steve Heiskary, lake expert with the Minnesota Pollution Control Agency.

This year, the heavy rains in May and June washed a large amount of nutrients into Minnesota lakes and streams. Those nutrients, including phosphorus, help feed the algae growth.

"A lot of the lakes are turning green this year where they didn't last year," said Gerry Maciej, Benton Soil and Water Conservation District manager.

In June, a dog's death after swimming in Prairie Lake near Clear Lake prompted warnings about the potential dangers of blue-green algae.

Blue-green algae blooms are thick and cloudy, and can look like green paint, pea soup or floating mats of scum. Some contain toxins that can be deadly to dogs and other animals. In humans, they can cause nausea and irritation of the skin, eye, nose and throat.

Little Rock Lake near Rice, where some blue-green algae growth occurs every year, was the source of calls and complaints in recent weeks about odor. The county responded by posting information and resources on its website about blue-green algae.

"It was pretty much all over the lake," said Julie Fandel, president of the Little Rock Lake Association.

But the rain that fell earlier this week seems to have helped clear out the algae, Fandel said. And it didn't stop people from boating, tubing and otherwise enjoying the lake, she said.

Blue-green algae thrive in warm water, Heiskary said. When the temperature of a lake climbs above 75 or 80 degrees, blue-green forms start to have a competitive advantage over other forms of algae, he said.

Heiskary said he hasn't heard of other dog deaths or severe blue-green algae outbreaks around the state. However, it's not unusual to see such blooms into late September and early October depending on the weather, he said.

This year, the MPCA has received calls and comments about the algae on lakes that have not typically experienced blooms, Heiskary said.